Key Ring Research Articles

Synthetic Study toward Daphnimacropodines.

Daphnimacropodines A-C are members of a small but structurally distinct subfamily of Daphniphyllum alkaloids. Their congested polycyclic skeletons, and two vicinal quaternary stereocenters, present significant synthetic challenges. This paper describes two stereoselective approaches to constructing the tricyclic core structures of daphnimacropodines, achieved through a straightforward Rh-catalyzed [4 + 3] cycloaddition using simple building blocks. This work also highlights an intramolecular Heck reaction that rapidly assembles the cyclohexane ring moiety, a Tsuji-Trost allylation that forged the critical C-8 quaternary stereocenter, an efficient hetero-Diels-Alder reaction, and an intramolecular nucleophilic addition, which paved the way to the key cyclopentane ring. The assembly of the tetrahydropyrrole motif was also investigated.

Cavity induced modulation of intramolecular vibrational energy flow pathways.

Recent experiments in polariton chemistry indicate that reaction rates can be significantly enhanced or suppressed inside an optical cavity. One possible explanation for the rate modulation involves the cavity mode altering the intramolecular vibrational energy redistribution (IVR) pathways by coupling to specific molecular vibrations in the vibrational strong coupling (VSC) regime. However, the mechanism for such a cavity-mediated modulation of IVR is yet to be understood. In a recent study, Ahn et al. [Science 380, 1165 (2023)] observed that the rate of alcoholysis of phenyl isocyanate (PHI) is considerably suppressed when the cavity mode is tuned to be resonant with the isocyanate (NCO) stretching mode of PHI. Here, we analyze the quantum and classical IVR dynamics of a model effective Hamiltonian for PHI involving the high-frequency NCO-stretch mode and two of the key low-frequency phenyl ring modes. We compute various indicators of the extent of IVR in the cavity-molecule system and show that tuning the cavity frequency to the NCO-stretching mode strongly perturbs the cavity-free IVR pathways. Subsequent IVR dynamics involving the cavity and the molecular anharmonic resonances lead to efficient scrambling of an initial NCO-stretching overtone state over the molecular quantum number space. We also show that the hybrid light-matter states of the effective Hamiltonian undergo a localization-delocalization transition in the VSC regime.

Total Synthesis Analysis of Pseuboyenes D

In this work, we propose a total synthesis route for the antifungal agent Pseuboyenes D, a compound derived from Pseudallescheria boydii CS-793. Pseuboyenes D exhibits antifungal activity comparable to Amphotericin B while offering the advantage of a simpler structure, making it a promising candidate for clinical applications. The system became the focus of this analysis due to its regioselectivity, and after exploration, a [2+2] photocycloaddition and ring expansion strategy was adopted to construct the key bridged ring system. The route employs readily available substrates and mild reaction conditions, making it scalable and suitable for large-scale production. Computational analysis of the regioselectivity of the photocycloaddition revealed that the bridged adduct was thermodynamically favored over the fused system. The synthetic route was further diversified by incorporating functional group modifications using TMS derivatives, enhancing the potential for pharmacological applications. Overall, this work establishes an efficient and scalable synthetic pathway for Pseuboyenes D, paving the way for future applications in antifungal drug development.

Fano mode based plasmonic sensor for temperature and chemical pollutant detection

Plasmonic sensors provide great sensitivity to minute quantities of analytes and provide excellent detection. In present context of environmental monitoring, plasmonic sensor can prove to be an excellent choice in chemical pollutant and temperature detection. Plasmonic sensors can provide immediate results, allowing for monitoring temperature changes in ecosystems or climate studies and quick decision-making in emergency situations related chemical pollution incidents. They are compact and can be integrated into portable devices for on-site analysis. In this investigation, a plasmonic refractive index sensor based on key ring shaped resonator consisting of a microring resonator and two rectangular resonator is proposed. Finite-Difference Time-Domain (FDTD) method is used to study the transmittance characteristics of the sensor. The device exhibits quadruple Fano resonance with highest sensitivity of 2521.7 nm/RIU. Other performance parameters such as figure of Merit (FOM), Quality (Q) factor and Detection limit (DL) are also been calculated, with values 98.8 RIU−1, 99.6 and 0.01 respectively. Additionally, the effects of different geometrical configurations is also studied, providing insights into the design principles in context of potential fabrication complexities. Further, the simulated Fano characteristic is validated against the theoretical value. The application of the proposed sensor is investigated for different types of analyte such as chemical pollutants and temperature sensing.

Total Synthesis of Homoseongomycin Enantiomers and Evaluation of Their Optical Rotation.

A total synthesis of each homoseongomycin enantiomer was accomplished in 17 total steps (longest linear sequence = 12 steps) and 10 chromatographic purifications. Several schemes were attempted to forge the key 5-membered ring, but only a Suzuki coupling-intramolecular Friedel-Crafts acylation sequence proved viable. Challenges encountered during the optical rotation characterization of the natural product left us with two important takeaways. First, highly colored compounds like homoseongomycin that absorb near/at the sodium d-line may require optical rotation measurements at other wavelengths. Second, high dilution of such compounds to obtain measurement at the sodium d-line could result in artificially large and incorrectly assigned specific rotations. To verify the optical rotation, electronic circular dichroism spectra were acquired for both homoseongomycin enantiomers and were transformed into optical rotary dispersions via the Kramers-Kronig transform. We note the wavelength dependency on rotation, and at the sodium d-line 589 nm, we reassign the optical rotation of L-homoseongomycin from (-) to (+).

Studies on the effects of preheated β-lactoglobulin on the physicochemical properties of theaflavin-3,3′-digallate and the interaction mechanism

Teaflavin-3,3′-digallate (TFDG) is a sensory and health benefit substance in tea beverage, but is usually eliminated during processing due to the formation of tea cream by binding with proteins. In order to retain the TFDG, β-lactoglobulin (β-LG) was used to bind with TFDG and avoid the formation of tea cream. The results of physicochemical tests and entropy weight-TOPSIS showed that the best β-LG-TFDG dispersion (TFDG concentration: 0.468 g/L) had low particle size (37.29 nm), high electrical potential (−32.43 mv), high transmittance (88.52%), and strong antioxidant activity (84.82%), when the preheated temperature of β-LG was 85 °C and the molar ratio was 1:2. The multispectral experiment results showed that TFDG interacted with β-LG via static quenching, and preheated treatment of β-LG enhanced the interaction between β-LG and TFDG. CD spectroscopy suggested that TFDG induced slight changes in the secondary structure of β-LG. The results of molecular dynamics showed that preheated treatment leading in the changes in tertiary structure of β-LG, opening of key ring region of β-LG and exposing the active cavities of β-LG, which enhances the intermolecular forces between TFDG and β-LG. What's more, molecular docking was proved that preheated treatment of β-LG enhances the hydrophobic interactions and hydrogen bonds, which dominated the interaction between TFDG and β-LG. The results proposed in this research could further reducing tea cream formation and improving the healthy and sensory performances of tea beverage by using preheated β-LG without preserving both the tea pigments and the active nutrients.

One-pot synthesis of fused-rings heterocyclic systems based on symmetrically benzofuran annulated 1,8-naphthalimides

A useful and straightforward synthetic approach to afford heteroarenes by symmetrical annulation of two benzofuran units to 1,8-naphthalene anhydrides, through a regioselective one-pot Sn–Ar/C–H activation tandem reaction is introduced herein. Two synthetic pathways are compared, highlighting that the utilization of diester derivatives improves: (i) the compatibility with the key ring expansion step, (ii) the solubility of the intermediate thus facilitating its purification, and (iii) the versatility of the final imidization. The electrochemical and spectral properties of this new class of compounds are investigated.

Thermal stabilization of recycled PLA for 3D printing by addition of charcoal

Poly(lactic acid) (PLA) is one of the most widely used thermoplastic materials for 3D printing, particularly in the Fused Filament Fabrication technique. However, the printing process generates waste products and even though PLA is compostable, the possibility of recycling it provides ecological and economical benefits. In this work, a study on the stabilization of recycled PLA using charcoal (CC) was carried out, with the aim of overcoming the well-known problem of degradation (reduction in molecular weight) of PLA, during remelting. Microscopic investigations showed good dispersion of the filler in the polymer matrix, as well as better adhesion between the printed layers. Thermal analyses (Differential scanning calorimetry and thermogravimetry) indicate a stabilization of PLA waste because of the addition of small concentrations of CC to the recycled polymer matrix. These data are confirmed by GPC analyses, which show that the addition of filler is associated with higher molecular weight. Mechanical analysis indicated improved elongation at break and elasticity. Finally, a key ring was printed as an example of the better printability of the filament containing CC. The results indicate that a stabilization of the recycled PLA with a very low concentration of CC has been achieved. Improved 3D printability and properties of the 3D printed objects can be attained through recycling and recovery of wasted PLA, according to sustainability and circular economy matters.

Ring Expansion Strategies for the Synthesis of Medium Sized Ring and Macrocyclic Sulfonamides

AbstractTwo new ring expansion strategies are reported for the synthesis of medium sized ring and macrocyclic sulfonamides. Both methods can be performed without using classical protecting groups, with the key ring expansion step initiated by nitro reduction and amine conjugate addition respectively. Each method can be used to make diversely functionalised cyclic sulfonamides in good to excellent yields, in a range of ring sizes. The ring size dependency of the synthetic reactions is in good agreement with the outcomes modelled by Density Functional Theory calculations.

Ring Expansion Strategies for the Synthesis of Medium Sized Ring and Macrocyclic Sulfonamides.

Two new ring expansion strategies are reported for the synthesis of medium sized ring and macrocyclic sulfonamides. Both methods can be performed without using classical protecting groups, with the key ring expansion step initiated by nitro reduction and amine conjugate addition respectively. Each method can be used to make diversely functionalised cyclic sulfonamides in good to excellent yields, in a range of ring sizes. The ring size dependency of the synthetic reactions is in good agreement with the outcomes modelled by Density Functional Theory calculations.

Synthesis of a Pyridoazepine Scaffold via Rhodium-Catalyzed Ring Expansion and Nitroacetamide Condensation

Pyridoazepines are privileged structures in the search for novel drug candidates. We present the synthesis of a versatile pyridoazepine scaffold employing a precedented rhodium(II)-catalyzed ring expansion and subsequent double-condensation-cyclization with nitroacetamide. The reactions applied several potentially hazardous reagents and intermediates, including p-toluenesulfonyl azide and nitroacetamide, the latter of which was determined to be potentially explosive and shock-sensitive. Reactions employed were derisked for laboratory scale work through DSC and TSU analysis in concert with optimization of reaction conditions. The key rhodium-catalyzed ring expansion was shown by TSU analysis to occur in a controllable manner with manageable nitrogen evolution. A new procedure is presented that enables preparation of nitroacetamide without excessive manipulation (i.e., extractive isolation) or isolation of dry solid. This article describes early safety studies used to derisk the preparation of multi-gram quantities of the target pyridoazepine.

Finite element analysis and fatigue characteristics of ring die

The ring die granulator is a piece of important equipment in the feed industry. In order to optimize the performance of its key component ring die, the force and action area of the die hole and the inner surface of the ring die are analyzed and solved during the operation of the ring die. Three different die hole layouts and three different widths of ring die are established, and the finite element simulation is carried out. The influence of the above two factors on the strength of the ring die is studied by analyzing the stress and the displacement data. Based on theMonte Carlo method, the probability density function of the random load was derived to obtain the cyclic variation model of ring mode load, and the multi-axis fatigue simulation analysis of ring mode was carried out according to the obtained model. The result shows that the fatigue failure area of the ring die was most likely to occur near the die hole of the restraint end during the pelleting process. Improvement measures were put forward for the ring die structure, and the ring dies life is significantly improved.

Proteomic response of Pseudomonas aeruginosa IIPIS-8 during rapid and efficient degradation of naphthalene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the ecosystem and are of significant concern due to their toxicity and mutagenicity. Bioremediation of PAHs is a popular and benign approach that ameliorates the environment. This study investigated the biodegradation and proteome response of Pseudomonas aeruginosa IIPIS-8 for two-ringed PAH: naphthalene (NAP) to understand proteome alteration during its bioremediation. Rapid biodegradation was observed up to 98 ± 1.26% and 84 ± 1.03%, respectively, for initial concentrations of 100 mg L−1 and 500 mg L−1 of NAP. Degradation followed first-order kinetics with rate constants of 0.12 h−1 and 0.06 h−1 and half-life (t1/2) of 5.7 h and 11.3 h, respectively. Additionally, the occurrence of key ring cleavage and linear chain intermediates, 2,3,4,5,6, -pentamethyl acetophenone, 1-octanol 2-butyl, and hexadecanoic acid supported complete NAP degradation. Proteomics study of IIPIS-8 throws light on the impact of protein expression, in which 415 proteins were quantified in sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) analysis, of which 97 were found to be significantly up-regulated and 75 were significantly down-regulated by ≥ 2-fold change (p values ≤ 0.05), during the NAP degradation. The study also listed the up-regulation of several enzymes, including oxido-reductases, hydrolases, and catalases, potentially involved in NAP degradation. Overall, differential protein expression, through proteomics study, demonstrated IIPIS-8's capability to efficiently assimilate NAP in their metabolic pathways even in a high concentration of NAP.

An Improved Lattice-Based Ring Signature With Unclaimable Anonymity in the Standard Model

Abstract Ring signatures enable a user to sign messages on behalf of an arbitrary set of users, called the ring, without revealing exactly which member of that ring actually generated the signature. The signer-anonymity property makes ring signatures have been an active research topic. Recently, Park and Sealfon (PS; CRYPTO’19) presented an important anonymity notion named signer-unclaimability and constructed a lattice-based ring signature scheme with unclaimable anonymity in the standard model; however, it did not consider the unforgeable w.r.t. adversarially chosen-key attack (the public key ring of a signature may contain keys created by an adversary) and the signature size grows quadratically in the size of ring and message. In this work, we propose a new lattice-based ring signature scheme with unclaimable anonymity in the standard model. In particular, our work improves the security and efficiency of PS work, which is unforgeable w.r.t. adversarially chosen-key attack, and the ring signature size grows linearly in the ring size.

A Multiple Badge Architectures Open Source RFID Reader with Insight Regarding Room Occupants

The preferred architecture and the source company for radio frequency identification (RFID) badge access cards can vary over time within the same company, depending on what management may envision for the future of working. Additionally, the preferred badge architecture and the company that makes those badges can vary from company to company, and from original equipment manufacturer (OEM) to their supplier partners. These circumstances create some inefficiencies amongst the workforce. Within the same engineering campus of a large OEM, many employees may still have the old key ring style badge, but some of the new RFID device readers may no longer accept this outdated badge architecture, which means these employees may not have access to certain areas until they get their new smart badge ID card. This makes doing their job much more difficult, potentially forcing them to find new ways to access the room or area that they need. Additionally, due to differences in badge architecture, an OEM’s supplier partners do not have access to areas of the OEM’s testing site or offices, even ones in which the OEM would prefer that they have permission to access in order to increase work efficiency (including test tracks and special laboratories). This paper presents a new open sourced RFID card reader which is designed, tested and implemented to read both of the most popular badge architectures (key ring badges and smart cards). The new proposed system also includes a unique function which shows the employee more information about the occupants inside of the room that they are trying to access. After reflecting on the state-of-the-art, the main selling point of the proposed system is that it recognizes multiple different badge architectures, and it doesn’t require the end user to source their RFID devices from a certain company. It provides other benefits including allowing suppliers and OEMs to seamlessly share collaborative spaces, and ensuring older versions of badges don’t become obsolete.

Quantum chemistry study on the promoted reactivity of substituted cyclooctynes in bioorthogonal cycloaddition reactions

AbstractIn the present research, we focus on the energetics and electronic aspects of enhanced reactivity in the regioselective bioorthogonal 1,3-dipolar cycloaddition reaction of various substituted cyclooctynes with methyl azide, applying quantum chemistry approaches. In this respect, we assessed the structural and energetic properties of regioisomeric products and their corresponded transition states and calculated the reaction electronic energy changes and energy barriers through the cycloaddition pathways. The obtained results revealed that the trifluoromethyl substitution and fluorination of cyclooctynes lead to improved reactivity, in conjunction with increased exothermicity and decreased activation energy values. On the other hand, quantum theory of atoms in molecules computations were performed on some key bond and ring critical points that demonstrated the stabilizing topological properties of electron density and its derivatives upon trifluoromethyl substitution and fluorination of propargylic carbon of cyclooctynes which can be regarded as the essential origin of enhanced reactivity.

Boosting Palladium-Catalyzed Aryl-Nitro Bond Activation Reaction by Understanding the Electronic, Electrostatic, and Polarization Effect: A Computational Study from a Basic Understanding to Ligand Design.

Although palladium-catalyzed aryl-nitro bond activation reaction has recently gained a lot of interest, it still requires rather harsh conditions. We here systematically explore the substituent effect on oxidative addition steps, known as the rate-determining step, by density functional theory simulations based on a Nakao's nitrogen heterocyclic carbene (NHC) ligand. The key aryl ring on the catalyst, ring A, acts as a π-donor and stabilizes the palladium center of the transition state, and thus an electron-rich ring A is expected to lower the barrier. However, the polarization and electrostatic effects were shown to be more important, although they were often ignored before. These effects originate from through-space interaction with a nitro group in the resting state, and the overall effect is that any polarizable or partly negative group near ortho- or meta-site of ring A is harmful for the reaction. Based on these discoveries, we proposed a list of guidelines for successful ligand developments and designed several new ligands. These ligands exhibit a significantly lower barrier than the reported Nakao's ligand by as large as ∼5 kcal/mol, in both gas phase and solvent with a moderate dipole. These candidates will promote further experimental studies and enhance the ability to improve ligands in a rational and predictive manner.

A new design of small-sized magnetorheological brakes based on the mixed mode operation for high torque efficiency

A small-sized brake generating the torque less than 0.5 Nm is very attractive to achieve desired dynamic motions in many different fields such as medical haptic and auto door closure. In this work, a controllable compact-sized brake utilizing a magnetorheological fluid (MRF) is proposed and its effectiveness is validated through simulation and experiment. Unlike conventional shear mode magnetorheological brake (MRB), a mixed mode MRB (M-MRB) featuring both the flow and shear mode operations is designed to obtain high torque efficiency in which both the key shape and ring shape structures play the significant role. Through these structures, the proposed M-MRB can provide higher torque with the relatively less amount of MRF than conventional shear mode MRB. The key shape structure is fixed to the rotor and shaft of MRB and rotates in same direction. Then, MRF on the front and back of the barrier is subjected to the pressure difference resulting in the field-dependent torque generation. To demonstrate the effectiveness of the proposed design concept, a small-sized M-MRB is designed and manufactured considering the required torque level and space constraint of auto door closure applicable to autonomous vehicle systems. It is identified through a reasonable comparison between the proposed M-MRB and conventional MRB that the proposed one can improve controllable torque range up to 325% with less MR fluid than conventional MRB.

Mild Intermolecular Synthesis of a Cyclopropane‐Containing Tricyclic Skeleton: Unusual Reactivity of Isobenzopyryliums

AbstractCyclopropanes embedded in a polycyclic bridged architecture are a versatile structural motif, but such complex frameworks often impose substantial synthetic challenges. Herein we introduce a new approach for the expedient access to such spring‐loaded strained systems via an exceptionally mild intermolecular convergent process between the readily available isobenzopyryliums and vinyl boronic acids. Different from the typical conventional approaches, our protocol does not involve the highly active carbenoid intermediates or strong conditions in order to overcome the disfavored kinetic and thermodynamic problems. Instead, the key cyclopropane ring was formed between the well‐positioned nucleophile and electrophile in the adduct from the regioselective [4+2] cycloaddition. Thus, this unusual process also represents a new reactivity of the versatile isobenzopyryliums. The choice of a Brønsted acid catalyst with proper acidity is crucial to the high efficiency and selectivity for this multiple bond‐forming process. The strained products are precursors to other useful synthetic building blocks.

Mild Intermolecular Synthesis of a Cyclopropane-Containing Tricyclic Skeleton: Unusual Reactivity of Isobenzopyryliums.

Cyclopropanes embedded in a polycyclic bridged architecture are a versatile structural motif, but such complex frameworks often impose substantial synthetic challenges. Herein we introduce a new approach for the expedient access to such spring-loaded strained systems via an exceptionally mild intermolecular convergent process between the readily available isobenzopyryliums and vinyl boronic acids. Different from the typical conventional approaches, our protocol does not involve the highly active carbenoid intermediates or strong conditions in order to overcome the disfavored kinetic and thermodynamic problems. Instead, the key cyclopropane ring was formed between the well-positioned nucleophile and electrophile in the adduct from the regioselective [4+2] cycloaddition. Thus, this unusual process also represents a new reactivity of the versatile isobenzopyryliums. The choice of a Brønsted acid catalyst with proper acidity is crucial to the high efficiency and selectivity for this multiple bond-forming process. The strained products are precursors to other useful synthetic building blocks.